Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$150.87	9.327%	$164.9416	$164.94	$164.95	$164.90
Purchase #2	$148.79	12.486%	$167.3679	$167.37	$167.35	$167.40
Purchase #3	$23.81	5.777%	$25.1855	$25.19	$25.20	$25.20
Purchase #4	$98.74	13.367%	$111.9386	$111.94	$111.95	$111.90
Purchase #5	$27.98	13.849%	$31.855	$31.86	$31.85	$31.90
Purchase #6	$80.41	4.361%	$83.9167	$83.92	$83.90	$83.90
Purchase #7	$37.29	10.488%	$41.201	$41.20	$41.20	$41.20
7 purchase totals =	$567.89		$626.4063	$626.42	$626.40	$626.40